St. Paraskevi is the patron Saint of eye health.
During the era when the Roman Empire was persecuting the Church, while she was young she gave away all her possessions and traveled around, evangelizing.
She was arrested and tortured, and thrown into a vat of boiling pitch, which did not, miraculously, affect her at all. The Emperor Pius, who was present, asked her by what magic she cooled the pitch. She threw him some of the hot pitch, which burned him and blinded his eyes. The Emperor screamed and pleaded for St. Parasceva to heal him. And she did. He immediately ended the persecution of Christians.
But after he died, the new Emperor, Marcus Aurelius, renewed the persecution. St Parasceva, who continued to preach, was arrested and thrown into a pit with a snake. She made the sign of the cross and immediately it died. Eventually Saint Parasceva was beheaded for Christ.
A story of healing: Once I was blind
A place of healing: Saint Paraskevi Greek Orthodox Shrine Church
See also: OCA: Martyr Parasceva of Rome
Icon from Paraskevi, the Righteous Martyr of Rome
We have found your sacred shrine to be a clinic of the soul, O holy one, and all we faithful now accord honor to you with our voices strong, devout Martyr Paraskevi extolled by all.
The voice of the Bridegroom called you as a bride, and gave you an incorruptible crown, O godly-minded and all glorious Paraskevi; and He enrolled you, as one worthy, together with the august martyrs and prizewinners. As you rejoice with them, remember us who observe your holy feast and who assemble in your church. For as we stand in it now, we soulfully offer up hymns to you, devout Martyr Paraskevi extolled by all.